add experimental variant support to inlang message format plugin

[samuelstroschein]

Context

The inlang message format needs variant support to prerelease paraglide js. Loris implemented something. I need to verify that everything works as expected.

• remove @inlang/sdk 1 from dependencies for v2
  • update tests
• update vitest

Observations

• bundle alias is not used (indicates that it's not plugin related and should be unbundled into own entity MESDK-239)

				alias: {},

• avoiding ids for variants and messages seems desirable to enable roundtrips https://discord.com/channels/897438559458430986/1285885983606177803/1286052950766129174
• importing bundles: NewBundle, messages: NewMessage, variants: NewVariant might be easier than importing nested bundles nested to avoid duplicate mapping code in every plugin

export const importFiles: NonNullable<(typeof plugin)["importFiles"]> = async ({ files }) => {
	const messages = files.flatMap(parseFile)
	const bundlesIndex: Record<string, any> = {}

	for (const message of messages) {
		if (bundlesIndex[message.bundleId] === undefined) {
			bundlesIndex[message.bundleId] = {
				id: message.bundleId,
				alias: {},
				messages: [message],
			}
		} else {
			bundlesIndex[message.bundleId].messages.push(message)
		}
	}

	const bundles = Object.values(bundlesIndex) as NewBundleNested[]

	return { bundles }
}

• what about exposing db? complexity stems from transforming the entities as the plugins needs it like groupBy or selectNested. that comes out of the box with kysely

	const messages = bundles.flatMap((bundle) => bundle.messages)

• nodeFs is not used in toBeImportedFiles removing it would remove all fs related things from plugins 🥳
• matching undefined is desirable

"username=*":
	"{username} has to download the app.",
"username=undefined": 
    "The person has to download the app.",

• renaming variant matchers leads to unstable ids aka duplicate variants. solving this seems out of proportion given that the lix host is around the corner.

[samuelstroschein]

It seems like paraglide provided an icu1 plugin to test variants. the inlang message format does not contain information for variant support yet. i will add variant support to the inlang message format, then release paraglide js

[samuelstroschein]

While building the plugin numerous discrepancies in the data structure emerged. See MESDK-237. The result is MESDK-238